2. Estimate roundness (using comparative chart) and elongation
of the grains, and note how related to size and composition. Note
that three-dimensional shape measures can not be determined in
thin section.

For each grain type record its percentage, distribution and
orientation in the slide, and any correlation between composition,
size, shape, and alteration. Note also overgrowths, coatings,
nuclei, inclusions, special optical properties, etc...

5. Composition and type of cement, or detrital matrix, or both.
Percentage of whole rock.

7. Classify rock using scheme provided. Note that, when using
triangular diagrams, the percentages of the three end members must
sum to 100.

Interpretation

From your observations you should be able to draw some conclusions
about the origin of the rock. It must be realized, however, that full
interpretation of the origin of sedimentary rocks must result from a
compilation of all types of sedimentary information. In particular,
knowledge of fossils, sedimentary structures, laterally equivalent
and vertically adjacent lithofacies is essential. However, the
following comments may be useful:

A. Source area

A mineralogical immature sediment may give an idea of rock types in
the source area, and also indicate uplift and rapid erosion from high
relief (minimal weathering and abrasion). A mature mineralogy
commonly reflects recycling, although intense chemical weathering in
hot humid lowland areas may be responsible in a single cycle.

B. Transportation and depositional environment

Terrigenous sediments:

A single grain size measure is not diagnostic of nature
of transport except to indicate minimum competence of transporting
fluid. Vertical and lateral variations in sedimentary structures
and grain size are more useful here. However, thick
conglomeratic/breccia sections indicate large gradients and
proximity to source.
Abrasion (hence rounding and removal of mechanically unstable
grains) is minimal for sand sizes (except when wind blown) but
appreciable for gravel sizes. Hence good rounding in sands is
mostly inherited. Unweathered and rounded unstable grains probably
indicate substantial abrasion during a single sedimentary cycle,
whereas weathered rounded unstable grains probably indicate
weathering was an important factor in the rounding.
The clay content and sorting reflect final depositional
setting.

Chemical/biogenic sediments:

The texture of chemical/biogenic grains can only give an
idea of the nature of transportation if an in situ origin can be
ruled out, e.g. ooliths and intraclasts with a sparry calcite
cement. Carbonate sediments may be produced in situ with angular
or rounded grains, with or without matrix of micrite. However
presence of micrite normally implies an absence of current
reworking, but the converse is not true.
The nature of grains themselves can give a good idea of
depositional environment (e.g. fossils, glauconite).

C. Diagenetic History

Timing of cementation, dissolution, recrystallization. Some
diagenetic textures and early diagenetic minerals can give an idea of
depositional environment (e.g. calcite cements, dolomite, iron
minerals, etc...). Some detrital matrix (if any) may be post
depositionally filtered in or result from breakdown of volcanic or
sedimentary rock fragments.